Fixing a Constantly Running Toilet: Causes and Solutions

That constant hissing sound from your bathroom? It’s more than just annoying. A running toilet can waste up to 200 gallons of water per day, and if you’re a homeowner in Arvada or the surrounding Denver area, that’s money literally going down the drain.

At Honest Plumbing, we fix running toilets all the time for folks across Arvada, Wheat Ridge, Westminster, and greater Denver. And here’s the thing: most running toilet issues come down to just a few common culprits. Sometimes it’s an easy DIY fix. Other times, you’ll want a professional to step in. Either way, understanding what’s happening inside that tank puts you in control.

Let’s walk through why your toilet keeps running, how to figure out what’s wrong, and what you can do about it.

Why Your Toilet Keeps Running

Before you can fix a running toilet, you need to understand what’s actually happening inside the tank. There are really only three main components that cause this problem, and once you know what to look for, diagnosing the issue becomes a lot simpler.

Faulty Flapper Valve

The flapper is that rubber piece at the bottom of your tank that lifts when you flush and seals shut to let the tank refill. Over time, flappers get worn out. They crack, warp, or develop mineral buildup from our Colorado hard water. When the flapper doesn’t seal properly, water slowly leaks from the tank into the bowl. Your toilet senses the water level dropping and keeps trying to refill. That’s the running sound you hear.

Another flapper-related issue? The chain. If the chain connecting the flapper to the flush handle is too tight, it holds the flapper slightly open. Even a tiny gap lets water escape continuously.

Float Problems

The float is what tells your toilet when to stop filling. It rises with the water level, and once it reaches a certain height, it signals the fill valve to shut off. Simple enough, right?

Problems happen when the float is set too high or gets stuck. If it’s positioned too high, water rises past the fill line and pours into the overflow tube. The tank never actually “fills” in the system’s mind, so it just keeps running. Older toilets often have ball floats on arms that can get waterlogged or corroded. Newer toilets typically use a float cup that slides up and down the fill valve, but these can stick too.

Fill Valve Issues

The fill valve controls the flow of fresh water into your tank after each flush. When this component wears out or gets clogged with debris and mineral deposits, it may not shut off completely. You’ll hear water constantly trickling or hissing, even when the tank appears full.

In Arvada and throughout the Denver metro area, we deal with moderately hard water. That mineral content builds up inside valves over time, causing them to stick or leak internally. Sometimes a good cleaning fixes the problem. Other times, the whole valve needs replacing.

How to Diagnose the Problem

Figuring out which component is causing your running toilet isn’t complicated. Here’s a quick diagnostic process:

1. Remove the tank lid and set it somewhere safe (porcelain chips easily).
2. Flush the toilet and watch what happens. Pay attention to where the water goes and when the running sound occurs.
3. Check the water level. Is it rising up to or into the overflow tube? If yes, your float or fill valve is the likely culprit.
4. Look at the flapper. Is water trickling from the tank into the bowl even when nothing is happening? Try pressing down gently on the flapper. If the running stops, you’ve found your problem.
5. Listen to the fill valve. If you hear hissing or see water spraying inside the tank even after it should have stopped filling, the fill valve is probably failing.

A simple food coloring test can also help identify flapper issues. Add a few drops of food coloring to the tank water and wait 15-20 minutes without flushing. If the color appears in the bowl, water is leaking past the flapper.

For homeowners in Arvada and nearby communities like Wheat Ridge, these diagnostic steps usually point to one clear problem. But if you’re seeing multiple issues or the cause isn’t obvious, that’s when calling a professional makes sense.

Step-by-Step Repair Guide

Once you’ve identified the problem, many running toilet repairs are doable for the average homeowner. Here’s how to tackle the three most common fixes.

Replacing the Flapper

This is the most frequent fix and probably the easiest.

1. Turn off the water supply by twisting the shutoff valve (usually located behind and below the toilet) clockwise.
2. Flush the toilet to drain most of the water from the tank. Use a sponge to soak up any remaining water.
3. Remove the old flapper. Unhook the chain from the flush lever. Most flappers have side tabs that slip off the overflow tube or pins on the flush valve. Just pull them free.
4. Take the old flapper to the hardware store. Flappers come in 2-inch and 3-inch sizes, and matching the right one matters. If you can’t bring it with you, check your toilet model number and look it up.
5. Install the new flapper. Clip the side tabs onto the overflow tube or pins, then reconnect the chain to the flush lever. Leave about half an inch of slack in the chain so it can seat fully but still lift the flapper completely when you flush.
6. Turn the water back on and test. The tank should fill and stop, with no running or leaking.

Adjusting or Replacing the Float

If your water level is too high and running into the overflow tube, start by adjusting the float.

For ball floats (the round ball on an arm): Bend the metal arm down slightly to lower the float position, or turn the adjustment screw if there is one.

For float cups (the cylinder that rides on the fill valve): Look for a pinch clip or adjustment screw on the side of the fill valve. Squeeze the clip and slide the float down, or turn the screw to lower the water level.

Your goal is to have the water stop about half an inch to one inch below the top of the overflow tube. Flush a few times to make sure the adjustment holds.

If adjusting doesn’t work and the float seems stuck or damaged, it’s usually easier to replace the entire fill valve assembly (see below) rather than just the float.

Installing a New Fill Valve

When cleaning and adjusting don’t solve fill valve problems, replacement is the answer. Fill valves are inexpensive (usually under $20) and come in universal sizes that fit most toilets.

1. Shut off the water supply and flush to empty the tank. Sponge out remaining water.
2. Disconnect the water supply line from the bottom of the tank. Have a bucket and towels ready because some water will spill.
3. Remove the old fill valve. There’s a large locking nut under the tank holding it in place. Unscrew it (may require pliers or an adjustable wrench) and lift out the old valve from inside the tank.
4. Adjust the new fill valve height according to the package instructions. Most modern fill valves are adjustable to fit different tank sizes. The top of the valve should sit about an inch higher than the overflow tube.
5. Insert the new valve through the hole in the bottom of the tank. Tighten the locking nut by hand, then give it a quarter turn with pliers. Don’t overtighten or you could crack the tank.
6. Reconnect the water supply line. Again, hand-tight plus a little snug with pliers.
7. Connect the refill tube (the small flexible tube) to the overflow tube. This directs a small amount of water into the bowl during filling.
8. Turn on the water and test. Adjust the float if needed so water stops at the proper level.

Tools and Materials You Will Need

Good news: fixing a running toilet doesn’t require a bunch of specialized tools. Most Arvada homeowners already have what they need.

Basic Tools:

• Adjustable wrench or channel-lock pliers
• Flathead and Phillips screwdrivers
• Sponge or old towels
• Bucket
• Flashlight (tank interiors can be hard to see)

Replacement Parts:

• Flapper valve (make sure to match the 2″ or 3″ size for your toilet)
• Fill valve kit (universal kits work for most toilets)
• Wax ring (only if you need to remove the toilet entirely, which is rare for running toilet issues)

Optional but Helpful:

• Food coloring for leak testing
• White vinegar for cleaning mineral deposits
• Rubber gloves

You’ll find all these supplies at any hardware store in Arvada or the Denver area. If you’re unsure which parts to buy, snap a photo of your toilet model number (usually stamped inside the tank or on the back of the bowl) and bring it with you.

When to Call a Plumber

DIY repairs work great for straightforward flapper, float, and fill valve problems. But some situations call for professional help.

You should call a plumber if:

• The tank or bowl is cracked. A cracked tank can’t be reliably repaired and will eventually leak or break completely. Toilet replacement is the only real solution.
• The flush valve seat is corroded. This is the surface the flapper seals against. If it’s pitted or rough, even a new flapper won’t seal properly. Sometimes the seat can be repaired with a kit, but often the toilet needs replacing.
• Water is leaking from the base of the toilet. This indicates a failed wax ring seal, which requires removing the entire toilet to fix.
• You can’t locate the shutoff valve or it won’t close. Older homes in Arvada, Westminster, and parts of Denver sometimes have corroded or stuck shutoff valves. Forcing them can cause bigger problems.
• You’ve replaced parts and the toilet still runs. If you’ve gone through the diagnostic steps and swapped components but the problem persists, something less obvious may be going on.
• Your supply lines are old or brittle. Older braided steel or plastic supply lines can fail without warning. If yours look questionable, it’s worth having a professional assess the situation.

At Honest Plumbing, we handle all types of toilet repairs for homeowners across Arvada and the surrounding communities. Sometimes people call us after attempting a DIY fix that didn’t quite work out. No judgment there. We’re happy to step in and get things sorted.

Preventing Future Toilet Problems

Once you’ve fixed your running toilet, a little maintenance goes a long way toward preventing the problem from coming back.

Inspect components periodically. Every six months or so, lift the tank lid and take a look. Check the flapper for signs of wear, warping, or mineral buildup. Make sure the float moves freely and the fill valve isn’t hissing.

Replace flappers proactively. Even if your flapper seems fine, they typically only last 3-5 years. Replacing one before it fails costs a few dollars and takes five minutes. Waiting until it causes problems can waste a lot of water.

Address hard water buildup. Colorado’s water leaves mineral deposits on everything, including toilet components. Occasionally cleaning the inside of your tank with white vinegar can help. Just pour a couple cups in, let it sit for an hour, then flush.

Keep the water supply valve functional. Turn your toilet’s shutoff valve fully open when in use. Once or twice a year, turn it off and on again to make sure it still works. Valves that sit in one position for years can seize up when you actually need them.

Don’t ignore small issues. If you hear occasional running or phantom flushes (the toilet refilling on its own), address it early. A small leak wastes water and signals a component that’s about to fail completely.

For homeowners in Arvada, Wheat Ridge, Westminster, and throughout the Denver metro, these simple habits can save significant money on water bills and prevent inconvenient breakdowns.

Conclusion

A running toilet is one of those problems that’s easy to ignore until you see your water bill. The good news is that most causes are straightforward to diagnose and fix. A worn flapper, a misadjusted float, or a failing fill valve accounts for the vast majority of cases. With basic tools and a little patience, many homeowners can handle these repairs themselves.

But if you’d rather not mess with it, or if the problem turns out to be something more complicated, that’s what we’re here for. Honest Plumbing serves Arvada, Denver, Wheat Ridge, Westminster, and the surrounding areas. We troubleshoot and repair all types of toilet issues, from simple fixes to complete replacements.

If your toilet won’t stop running and you want it fixed right, give us a call. We’ll get to the bottom of the problem and have your bathroom back to normal.

Frequently Asked Questions

Why does my toilet keep running constantly?

A constantly running toilet is typically caused by one of three components: a faulty flapper valve that doesn’t seal properly, a float set too high or stuck in position, or a worn fill valve that won’t shut off completely. Hard water mineral buildup can also contribute to these issues over time.

How do I fix a running toilet myself?

Start by diagnosing the problem—check if water is leaking past the flapper, if the water level is too high, or if the fill valve is hissing. Most fixes involve replacing the flapper, adjusting the float position, or installing a new fill valve. These repairs require basic tools and usually cost under $20 in parts.

How much water does a running toilet waste per day?

A running toilet can waste up to 200 gallons of water per day, which significantly increases your water bill. Even a small leak from a worn flapper allows water to continuously escape from the tank into the bowl, triggering constant refilling cycles.

How can I tell if my toilet flapper needs replacing?

Perform a simple food coloring test: add a few drops to the tank water and wait 15-20 minutes without flushing. If color appears in the bowl, your flapper is leaking. You should also visually inspect the flapper for cracks, warping, or mineral buildup that prevents a proper seal.

When should I call a plumber for a running toilet?

Call a professional if your tank or bowl is cracked, the flush valve seat is corroded, water leaks from the toilet base, the shutoff valve won’t close, or the problem persists after replacing parts. These issues require specialized expertise or toilet replacement.

How often should toilet components be replaced for maintenance?

Flappers typically last 3-5 years and should be replaced proactively before they fail. Inspect tank components every six months for wear, mineral buildup, or malfunction. Regular maintenance and addressing hard water deposits with white vinegar can extend the life of toilet parts.